DM-18667 Add support to display_firefly for obtaining and passing along an authorization token for Firefly

[stargaser]

• retrieve token from Display kwarg if provided; then from ACCESS_TOKEN environment variable
• pass token to FireflyClient factory methods
• add a section to the documentation explaining the token= kwarg

[tgoldina]

@xiuqin asked me to help verifying this ticket. I have verified it on JupyterHub in a local environment with display_firefly from your branch, firefly_client 2.2.0 locally installed.

It works as expected.

Below are more details on how I tested it.

I've tested it using unified portal app (which can act as a Firefly and SUIT server). It requires authorization to work.

import lsst.afw.display as afwDisplay
display1 = afwDisplay.Display(url='https://lsst-lsp-int.ncsa.illinois.edu/portal/app', frame=1, backend='firefly')
fc = display1.getClient()
fc.show_table(tbl_id='LSSTTAPSchemas', title='LSST TAP Schemas',
             file_on_server='https://lsst-lsp-int.ncsa.illinois.edu/api/tap/sync?REQUEST=doQuery&LANG=ADQL&QUERY=SELECT+*+FROM+TAP_SCHEMA.schemas',
             options=dict(removable=True, showUnits=False, showFilters=True))

Creating client with https://lsst-lsp-int.ncsa.illinois.edu/portal/app would fail, if not authorized. Also TAP service on lsst-lsp-int requires authorization.

With the default notebook firefly, the show_table above produces '401 Unauthorized error' as expected, because a generic firefly server does not have authorization mechanism set.